| Carbohydrate are the most inexpensive nutrients,which can be used to provide energy,save costs,reduce the consumption of protein as energy with appropriate amount for fish.Although the utilization of carbohydrate is low,the mechanism and utilization of carbohydrate metabolism are still at the initial stage,it has become a hot spot in the research of sustainable development of fisheries.In recent years,the mechanism of carbohydrate utilization in fish is mainly focused on the physiological indexes and the expression of glucose metabolism genes.In this study,carp was used as the research object,using the method of physiological and proteomic combination,using i TRAQ technology to study the expression of carp hepatopancreas protein with different glucose levels,it would have important theoretical and practical significance in revealing the carbohydrate utilization mechanism of carp from the protein level and reducing feed cost.The main research is divided into four parts:1.Effects of different corn starch levels on growth,body composition and digestive indexes of common carp(Cyprinus carpio)The experiment used single factor experiment design method,three diets were formulated containing three corn starch levels(0%,15%,30%)(30% crude protein of dry matter,crude fat 5.5% dry matter).The common carp(60.82±0.38 g)were fed for 8 weeks for measuring its growth,body composition and activities of digestive enzyme to study the effects of different levels of dietary corn starch on the growth.The results showed that growth rate(WG),specific growth rate(SGR),hepatosomatic index(HSI),crude protein content of muscle and liver glycogen of 30% corn starch treatment group were significantly higher than those in the 0% control group(P<0.05).There were no significant differences between 15% corn starch treatment group and 0% control group of these index(P>0.05).Protein efficiency(PER),crude fat of whole body of 30% and 15% corn starch treatment group were significantly higher than the 0% control group(P<0.05).Feed coefficient(FCR)is the opposite(P<0.05).With the increasing of dietary carbohydrate level,the activity of lipase(LPS)and amylase(AMS)in the intestine of carp showed an upward trend,but there was no significant difference between the two groups(P>0.05).The activity of protease(TRY)of 30% and 15% corn starch treatment group was significantly higher than that of the 0%control group(P<0.05).In conclusion,under the experimental conditions,high carbohydrateof diet can promote the growth of carp,spare protein.From digestive enzyme activity,high carbohydrate can improve the digestive ability of carp.It revealed that the digestibility of dietary protein,fat and carbohydrate increased and the metabolism and transformation of nutrients were enhanced.2.Effects of different corn starch levels on some immune indexes and hepatopancreas structure of common carp(Cyprinus carpio)Through determining some immune indexes and producing,observating hepatopancreas tissue slices of of carp study the effects of different corn starch levels on some immune indexes and hepatopancreas structure.The results showed that with the increasing of corn starch levels,serum immunoglobulin M(Ig M),total antioxidant capacity(T-AOC),the activity of CAT and alanine aminotransferase activity increased significantly(P<0.05);acid phosphatase(ACP)activity,SOD activity and CAT activity hepatopancreas increased significantly(P<0.05);CAT activity in head kidney were significantly increased(P<0.05),while lysozyme activity decreased significantly(P<0.05).Hepatopancreas tissue sections showed that the liver cells of 0% corn starch control group was normal;15% corn starch treatment group showed mild hydropic degeneration and fatty degeneration of liver cells;30%corn starch treatment group showed more severe fatty degeneration.To sum up,it can promote the specific immunity and antioxidant capacity of carp by increasing the level of carbohydrate in the diet,but it can inhibit the activity of lysozyme.3.Effects of different corn starch levels on physiological indexes and carbohydrate metabolism enzyme activity of common carp(Cyprinus carpio)By measuring the physiological indexes of blood and carbohydrate metabolism enzyme activity with enzyme-linked immunosorbent assay,the effects of different corn starch levels on physiological indexes and carbohydrate metabolism enzyme activity of common carp were studied.The results showed that with the increasing of carbohydrate levels,the glucose,triglyceride,total cholesterol and insulin of serum increased significantly(P<0.05),in addition to total cholesterol reached the maximum in 15% corn starch treatment group,others reached the maximum at 30% corn starch treatment group.Glucokinase(GK)activity of hepatopancreas reached a peak at 15% corn starch treatment group,but no significant difference with the control group(P>0.05).The activity of 6-phosphofructokinase(PFK)increased with the increase of the sugar level and trend.The activity ofphosphoenolpyruvate carboxykinase(PEPCK)decreased with carbohydrate increasing,but no significant difference in each group(P>0.05),1,6-fructose phosphatase(FBP)activity was significantly decreased(P<0.05);With carbohydrate levels increasing,liver glycogen synthase(GS)activity increased,while the activity of glycogen phosphorylase(GP)was opposite.In conclusion,the blood glucose and blood lipid increased with the increase of the sugar level.The results of carbohydrate metabolism enzyme activity showed that dietary carbohydrate can promote glycolytic enzymes and glycogen synthase activity,inhibition of gluconeogenesis and glycogen phosphorylase enzyme activity.The results showed that carp could make better use of carbohydrates,convert sugar into energy,and provide the activity for the organism.4.Analysis of differentially expressed proteins in the hepatopancreas of carp under different carbohydrate levels based on i TRAQBy the technology of i TRAQ 4695 proteins were identified from common carp hepatopancreas,and 660 differentially expressed.With the increasing of carbohydrate levels,333 proteins up-regulated and 309 proteins down-regulated,8 proteins first increased and then decreased,10 proteins first decreased and then increased.The results of GO and KEGG pathway analysis of the differentially expressed proteins in the hepatopancreas of Cyprinus carpio showed that the addition of carbohydrate to the diet had significant effects on the metabolism of term and metabolic pathway.With the increasing of the carbohydrate level,the expression of hexokinase(HK)and 6(PFK)were significantly increased,which significantly promoted the ability of glycolysis and provided energy for the body.The expression of fatty acid synthase increased significantly,indicating that part of the carbohydrate synthesis of fat,deposited in fish.The content of arginine and proline decreased,while the content of serine increased,indicating that the carbohydrate used for protein metabolism is mainly used for the accumulation of muscle protein,rather than the improvement of immunity.Increased levels of complement C3 and MHC class II promoted the phagocytosis of carp.The physiological and biochemical indexes of hepatopancreas proteins found that the carbohydrate of diet can promote the growth of carp,but it has a certain damage to the liver and pancreas of fish. |
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